The term Big Data has commonly been used for any sortof data flow which is larger than usual. Here, however, BigData refers to data sets and flows large enough to posesignificant challenges when using commonly available toolsand infrastructures to collect, manage and process thedata within a tolerable amount of time. Big Data is not justSlightly Larger Data, nor a question of sampling in largedata flows to be able to keep on as before. The point ofBig Data is that it changes the way we approach dataanalysis, inspiring entirely new families of informationservices and necessitating new processing models andknowledge representations. The challenges associatedwith handling Big Data are broadly due to four of itscharacterising properties: